Apparatus for capturing an object scene

ABSTRACT

An apparatus for capturing an object scene, in particular a seeking head for target-tracking missiles, such that, with a detector  86  in fixed relationship with a structure, it is possible to capture a large spatial angle. For that purpose the imaging optical system ( 30 ) has a system portion ( 28 ) facing the object scene which is pivotable with a pitch frame ( 24 ) about a pitch axis ( 26 ) perpendicular to a roll axis ( 18 ). The pitch frame ( 24 ) is mounted pivotably about the pitch axis ( 26 ) in a roll frame ( 16 ) which is supported in the structure ( 10 ) rotatably about the roll axis ( 18 ). The system portion ( 28 ) includes first beam deflection structure ( 36 ) by which the imaging beam path of the imaging optical system ( 30 ) is deflectable in a direction along the pitch axis ( 26 ). The imaging optical system ( 30 ) further includes second beam deflection structure ( 52 ) which are rotatable with the roll frame ( 16 ) and by which the deflected beam path is picked up along the pitch axis ( 26 ) and deflected in the direction of the roll axis ( 18 ). The detector ( 86 ) is arranged on the roll axis ( 18 ).

The invention concerns an apparatus for capturing an object scene,including an imaging optical system which is pivotable relative to astructure and a detector which is fixed with respect to the structureand on which an image of the object scene is produced by the imagingoptical system.

This apparatus may involve a seeking head for a target-tracking missile.The invention however can also be used in relation to an “all-aroundsearch arrangement”, that is to say a stationary apparatus by which alarge field of view is continuously scanned. Such an all-around searcharrangement is described and illustrated for example in EP 0 629 890 B1.

In known seeking heads for target-tracking missiles with a detectorwhich is fixed with respect to the structure, an imaging optical systemis supported cardanically about two axes which extend substantiallyperpendicularly to the longitudinal axis or roll axis of the missile,namely about a pitch axis and a yaw axis. In that way the optical systemcan be pivoted with two degrees of freedom about the detector which isfixed with respect to the structure, and oriented onto a target. Anexample of such a seeking head is described in DE 34 38 544 C2. In thatcase the squint angle of the seeking head, that is to say theinclination of the optical axis of the optical system relative to thelongitudinal axis of the missile, is limited by the mechanics of thecardanic support arrangement.

Seeking heads are known, in which an imaging optical system is carriedin a pitch frame which is pivotable about a pitch axis relative to aroll frame. The roll frame in turn is supported in the structure of themissile rotatably about a roll axis coincident with the longitudinalaxis of the missile (see DE 33 17 232 A1 and DE 198 24 899 C1). In thoseknown seeking heads the detector is not fixed with respect to thestructure but is provided on the pitch frame. That makes it difficult totake out the signals of the detector.

The object of the invention is to design an apparatus of the kind setforth in the opening part of this specification for capturing an objectscene, in such a way that, with a detector which is fixed with respectto structure, it is possible to detect a large spatial angle.

In accordance with the invention that object is attained in that

(a) the imaging optical system has an object-side system portion whichis pivotable with a pitch frame about a pitch axis perpendicular to aroll axis,

(b) the pitch frame is supported pivotably about the pitch axis in aroll frame which is supported rotatably about the roll axis in thestructure,

(c) the object-side system portion includes first beam deflection meansby which the imaging beam path of the imaging optical system can bedeflected in a direction along the pitch axis,

(d) the imaging optical system further includes second beam deflectionmeans which are rotatable with the roll frame and by which the deflectedbeam path is picked up along the pitch axis and deflected in thedirection of the roll axis, and

(e) the detector which is fixed with respect to the structure isarranged on the roll axis.

The use of a cardan system comprising the pitch frame and the roll framemakes it possible to capture a large spatial angle. In a suitablestructural configuration the object-side system portion can be pivotedwith respect to the roll frame about the pitch axis through more than90°, without that movement being impeded by the roll frame. The rotationof the roll frame about the roll axis permits orientation of the systemportion within an angle of 360°. In contrast to known roll-pitch systemshowever the detector is not arranged on the pitch frame but is arrangedfixedly with respect to the structure on the roll axis. That is madepossible by virtue of deflection of the imaging beam path. The imagingbeam path is firstly deflected by the first beam deflection means insuch a way that it extends along the pitch axis. The beam path is thennot influenced by pivotal movement of the object-side system portionabout the pitch axis, except for image rotation. The second beamdeflection means which are rotatable with the roll frame capture thebeam path deflected in that way, on the pitch axis, and deflect it insuch a way that it extends along the roll axis. The detector which isfixed with respect to the structure is disposed on the roll axis whichin fact is fixed with respect to the structure.

Embodiments of the invention are the subject-matter of the appendantclaims.

An embodiment by way of example of the invention is described in greaterdetail hereinafter with reference to the accompanying drawings in which:

FIG. 1 is diagrammatic broken-away view in longitudinal section of amissile with a seeking head,

FIG. 2 shows a modification of a detail of the imaging optical system,

FIG. 3 shows a further modification of a detail of the imaging opticalsystem, and

FIG. 4 shows another embodiment of the seeking head.

In FIG. 1 reference 10 denotes the structure of a target-trackingmissile. The nose of the missile is formed by a hemispherical dome orwindow 12. A seeking head 14 is disposed behind the dome 12.

The seeking head 14 has a roll frame 16. The roll frame 16 is supportedin bearing means 17 rotatably about a roll axis 18. This is indicated inFIG. 1 by the arrows 20. The roll axis 18 here coincides with thelongitudinal axis of the missile. A pitch frame 24 is supported in theroll frame 16 pivotably about the pitch axis 26 by way of bearing means22. The roll frame 16 permits a pivotal movement of the pitch frame andthe parts carried therein about the pitch axis 26 through an angle ofabout 180°, that is to say 90° rearwardly in FIG. 1 and 90° forwardly.

Carried in the pitch frame 24 is an object-side system portion 28 of animaging optical system which is generally identified by reference 30.The object-side system portion 28 includes a lens 32 which is mounted ina funnel-shaped holder 34 which is formed on the pitch frame, and firstbeam deflection means in the form of a deflection prism 36. Theobject-side system portion 28 of the imaging optical system 30 definesan optical axis 38. The optical axis 38 extends perpendicularly to thepitch axis 26. In the illustrated central position of the pitch frame 24the optical axis 38 coincides with the longitudinal axis of the missileand the roll axis 18. The roll axis 18, the pitch axis 26 and theoptical axis 38 intersect at the center point 40 of the curvature of thehemispherical dome 12. The cross-section of the deflection prism 36which is connected to the pitch frame 24 substantially forms anisosceles right triangle. The deflection prism 36 accordingly has a“hypotenuse surface” 42. That hypotenuse surface 42 forms an angle of45° with the optical axis 38. The imaging beam path of the imagingoptical system 30 is therefore deflected through 90° by total reflectionat the hypotenuse surface 42 so that the optical axis 44 of thedeflected beam path now coincides with the pitch axis 26. In thatsituation the beam path passes perpendicularly through the two “cathetussurfaces” 46 and 48 of the deflection prism 36. In the embodiment shownin FIG. 1 the cathetus surface 46 is convexly curved and cathetussurface 48 is concavely curved. As a result the deflection prism 36 hasa lens action. The deflection prism 36, in conjunction with the lens 32,produces an intermediate image 50 of the object scene.

The use of the deflection prism 36 as a lens reduces the number ofreflecting surfaces and thus light losses and scattered light. Inaddition the optical system can be passively temperature-compensated byclever choice of the prism materials and refractive powers.

The deflected imaging beam path is picked up by second beam deflectionmeans which are generally identified by reference 52. The second beamdeflection means 52 are supported fixedly in the roll frame 16 and arerotatable therewith about the roll axis 18. The second beam deflectionmeans 52 have a second deflection prism 54, a third deflection prism 56and a fourth deflection prism 58. The cross-sections of the deflectionprisms 54, 56 and 58, similarly to the deflection prism 36, areisosceles right triangles with hypotenuse surfaces at which the imagingbeam path is totally reflected and with cathetus surfaces which extendperpendicularly to the optical axis of the imaging beam path.

The second deflection prism 54 is disposed on the pitch axis 26. Itshypotenuse surface 60 is inclined at 45° relative to the pitch axis 26and to the once-deflected optical axis 44. A cathetus surface 62 isperpendicular to the optical axis 44 and is opposite to the cathetussurface 46 of the deflection prism 36. The intermediate image 50 is forexample between the cathetus surfaces 48 and 62. The imaging beam pathis deflected through 90° a second time by the deflection prism 54 sothat the twice-deflected optical axis 64 extends parallel to the rollaxis 18 in the plane defined by the pitch axis 26 and the roll axis 18.The twice-deflected optical axis 64 issues through the cathetus surface66 of the second deflection prism 54.

The third deflection prism 56 is disposed on the twice-deflected opticalaxis 64. Its hypotenuse surface 68 is again inclined at 45° relative tothe optical axis 64 and perpendicular to the hypotenuse surface 60 ofthe second deflection prism 54 and by total reflection again deflectsthe imaging beam path through 90° parallel to the pitch axis 26 inwardlytowards the roll axis 18. The triple-deflected optical axis 70 alsoextends in the plane defined by the pitch axis 26 and the roll axis 18.The entry-side cathetus surface 72 of the third deflection prism 56 isperpendicular to the twice-deflected optical axis 64 and opposite theexit-side cathetus surface 66 of the second deflection prism 54. Theexit-side cathetus surface 74 of the third deflection prism isperpendicular to the triple-deflected optical axis 70.

The second and the third deflection prisms 54 and 56 are carried withtheir hypotenuse surfaces in a roof-shaped holder 76 in the roll frame16.

The hypotenuse surface 78 of the fourth deflection prism 58 is parallelto the hypotenuse surface 68 of the third deflection prism 56 andinclined through 45° relative to the triple-deflected optical axis 70.The fourth deflection prism 58 is arranged in the roll frame 16 on theroll axis 18. Total reflection at the hypotenuse surface 78 causes theimaging beam path to be deflected through 90° a fourth time so that thequadruple-deflected optical axis 80 of the imaging beam path coincideswith the roll axis 18. The entry-side cathetus surface 82 of the fourthdeflection prism 58 is perpendicular to the triple-deflected opticalaxis 70 and is opposite the exit-side cathetus surface 74 of the thirddeflection prism. The exit-side cathetus surface 84 of the fourthdeflection prism 58 is towards a detector 86 which is fixed with respectto the structure.

The cathetus surfaces 62, 66, 72, 74, 82 and 84 are curved so that theassociated deflection prisms act at the same time as lenses. Thoselenses form a detector-side system portion of the imaging optical system30, by which an image 88 of the object scene is produced on the grid ofdetector elements of the detector 86.

The described arrangement operates as follows:

The pitch frame 24 permits a pivotal movement of the optical axis 38about the pitch axis 26 over an angle of about 90° forwardly andrearwardly in FIG. 1. The roll frame 16 permits a rotary movement of thepitch axis 26 about the roll axis 18 over an angle of 360°. As a result,the optical axis 36 can be oriented in any direction within thehemispherical spatial angle covered by the dome 12. Due to thedeflection of the beam path by the first deflection prism 36 the imagingbeam path is not influenced by the pivotal movement about the pitch axis26, except for image rotation. The imaging beam path falls on the seconddeflection prism 54, in any position of the pitch frame. The imagingbeam path is guided onto the stationary detector 86 by the deflectionprisms 54, 56 and 58, more specifically in any position of the rollframe 16. The arrangement of the detector, in fixed relationship withthe structure, facilitates signal transmission and the feed of coolantto the detector.

Intermediate imaging and the fact that the deflection prisms 54, 56 and58 are in the form of lenses makes it possible for the beamcross-section of the imaging beam path on passing through the deflectionprisms 54, 56 and 58 to be kept small.

Instead of the deflection prisms 36, 54, 56 and 58, it is also possibleto provide deflection mirrors. It is also possible for the deflectionprisms 54, 56 and 58 to be combined to form a single body 90, as isshown in FIG. 2.

As a difference in relation to the construction shown in FIG. 1 it isalso possible for the pitch axis to be displaced in a direction towardsthe detector and to be arranged along the beam path 70, in comparisonwith FIG. 1. When this design configuration is adopted, the reflectingmeans 54 and 56 shown in FIG. 1 are then arranged on the pitch frame andare pivotable therewith. In that case so-to-speak the first threereflecting means, shown in the form of deflection prisms 36, 54 and 56,then form the first beam deflection means of the object-side systemportion. In that case the intermediate image is produced between thethird and fourth reflecting means, in FIG. 1 approximately at the levelof reference numeral 70. In that case, as shown in FIG. 3, thedeflection prisms 36, 54 and 56 can be combined to form a single body.

The embodiment shown in FIG. 4 corresponds in principle to that shown inFIG. 1. Corresponding parts are denoted by the same references in FIG. 4as in FIG. 1.

In contrast to the embodiment of FIG. 1 the object-side system portionof the imaging optical system is a Cassegrain system with an annularhollow mirror 92 and a convex secondary mirror 94. An intermediate image96 is produced for example closely in front of the first deflectionprism 36. The deflection prisms 36, 54, 56 and 58 are respectively partsof cubes with a reflecting diagonal surface. A separate lens 98 producesthe image 100 of the object scene on the detector.

1. Apparatus for capturing an object scene, including an imaging opticalsystem (30) which is pivotable relative to a structure (10) and adetector (86) which is fixed with respect to the structure and on whichan image of the object scene is produced by the imaging optical system(30), characterized in that (a) the imaging optical system (30) a systemportion (28) facing the object scene which is pivotable with a pitchframe (24) about a pitch axis (26) perpendicular to a roll axis (18),(b) the pitch frame (24) is supported pivotably about the pitch axis(26) in a roll frame (16) which is supported rotatably about the rollaxis (18) in the structure (10), (c) the system portion (28) includesfirst beam deflection means by which the imaging beam path of theimaging optical system (30) is deflectable in a direction along thepitch axis (26), (d) the imaging optical system (30) further includessecond beam deflection means (52) which are rotatable with the rollframe (16) and by which the deflected beam path of the first beamdeflection means is picked up along the pitch axis (26) and deflected inthe direction of the roll axis (18), and (e) the detector (86) isarranged on the roll axis (18).
 2. Apparatus as set forth in claim 1characterized in that (a) the system portion (28) has the first beamdeflection means including first reflecting means (36) by which theimaging beam path of the imaging optical system (30) is deflectable in adirection along the pitch axis (26), (b) provided in the roll frame (16)and rotatable therewith on the pitch axis (26) are second reflectingmeans (54) by which the imaging beam path of the imaging optical system(30) is deflectable in a direction parallel to the roll axis (18), (c)provided in the roll frame (16) and rotatable therewith there are thirdreflecting means (56) by which the imaging beam path deflected in thatway is deflectable towards the roll axis (18) in a direction parallel tothe pitch axis (26), and (d) provided in the roll frame (16) androtatable therewith on the roll axis (18) are fourth reflecting means(58) by which the imaging beam path deflected by the third reflectingmeans (56) is deflectable in the direction of the roll axis (18) ontothe detector (86), the second, third and fourth reflecting means formingthe second beam deflection means (52).
 3. Apparatus as set forth inclaim 1 characterized in that (a) the system portion (28) in the pitchframe (24) has first reflecting means (36) by which the imaging beampath of the imaging optical system (30) is deflectable in a directionparallel to the pitch axis (26), (b) provided in the pitch frame (24) isa second reflecting means (54) by which the imaging beam path of theimaging optical system (30) is deflectable in a direction parallel tothe roll axis (18), (c) in the pitch frame (24) there is further a thirdreflecting means (54) by which the imaging beam path deflected in thatway deflected is deflectable towards the roll axis (18) in a directionalong the pitch axis (26), the first, second and third reflecting meansforming the first beam deflection means, and (d) in the roll frame (16)and rotatable therewith on the roll axis (18) as second beam deflectionmeans there are provided fourth reflecting means (58) by which theimaging beam path deflected by the third reflecting means (56) isdeflectable in the direction of the roll axis (18) onto the detector(86).
 4. Apparatus as set forth in claim 2 or claim 3 characterized inthat the reflecting means are deflection prisms (36, 65, 56, 58) of across-section substantially forming an isosceles right triangle, whosetotally reflecting hypotenuse surfaces (42, 60, 68, 78) deflect theimaging beam path, wherein the cathetus surfaces (62, 66; 72, 74; 82,84) are respectively perpendicular to the optical axis of the imagingbeam path.
 5. Apparatus as set forth in claim 4 characterized in that atleast a part of the cathetus surfaces form curved lens surfaces. 6.Apparatus as set forth in claim 4 characterized in that the plurality ofdeflection prisms forming the first or the second beam deflection meansare formed by a continuous body (90).
 7. Apparatus as set forth in claim2 or claim 3, characterized in that (a) the imaging optical system (30)is arranged behind a hemispherical dome (12), (b) the pitch and rollaxes (26, 18) perpendicularly intersect at the center point (40) ofcurvature of said dome (12), and (c) the reflecting surface of the firstreflecting means (36) extends at 45° relative to the roll axis (18)through said intersection point (40).
 8. Apparatus as set forth in oneof claims 1 through 3 characterized in that the imaging optical system(30) produces at least one intermediate image (50) in the region of thebeam deflection means (36, 52).
 9. Apparatus as set forth in claim 8characterized in that the intermediate image is produced by the systemportion (28) between the first and second beam deflection means (36,52).
 10. A missile which is equipped with an apparatus as set forth inclaim 1.